The invention relates to an apparatus for microlithographic projection exposure and to a method for determining a property of an arrangement which comprises an apparatus for microlithographic projection exposure and a substrate disposed in an exposure position of the apparatus. The invention further relates to an apparatus for inspecting a surface of a substrate and to a method for determining a property of an arrangement which comprises this type of inspection apparatus and a substrate. These types of inspection apparatuses include microscopes and optical inspection systems as used e.g. for the inspection of lithography masks or for the inspection of exposed wafers. Furthermore, they include optical systems for the calibration of mask patterning systems—so-called “registration units”—with which position marks can be measured with great precision on a lithography mask.
For the high precision imaging of micro- or nanostructures with the aid of a lithography exposure system it is important to know the position and the topography or the surface properties of the substrate to be exposed, e.g., in the form of a so-called wafer. In order to establish the position, focus sensors, for example, are used which, in direct proximity to a substrate table, guide a measurement signal such that it practically grazes the substrate plane and is then recaptured. In order to measure the substrate topography, measuring optics set up in parallel to the projection optics are often also used. This type of measuring optics is also called a “twin stage”. This type of measuring optics set up in parallel is associated with increased complexity because additional optics and also an additional displacement stage are required.
With regard to the use of these types of metrology systems the difficulty arises, in particular for lithography exposure systems which are operated in the EUV wavelength range (wavelength range of extreme ultraviolet radiation, e.g. 13.4 nm) that the working space of these systems on the substrate side is determined by the penultimate mirror in the beam path. From the optical point of view, it is advantageous if this space can be chosen to be particularly small. However, a very small working space only leaves a small amount of or even no installation space for a conventional focus sensor.